Although a current view of human speech sound perception argues for the use of "general mammalian auditory mechanisms", there is at present no extensive source of precise, comprehensive data comparing either the psychoacoustic or speech discrimination capacities of humans and other animals. As a start towards a more systematic study of the contribution of sensory vs. linguistic processes to speech perception, we propose a series of experiments designed to directly compare humans and monkeys in the discrimination and identification of speech and non-speech acoustic signals. Monkeys will be trained with operant conditioning techniques using positive reinforcement. A go, no-go procedure will be used for discrimination and a go-right, go-left procedure for identification. Humans and monkeys will be tested with identical stimuli and procedures. We already have preliminary data indicating that monkeys are much closer to humans in their capacity for intensity discrimination than for frequency discrimination. Accordingly, we have made predictions concerning the relative salience for humans and monkeys of speech sounds based on spectral vs. intensity cues. The ultimate objective is to precisely define both the quantitative and qualitative limitations of the monkey auditory-sensory system in relation to the human, in order to determine to what extent the monkey can provide an adequate model of human speech sound processing at the phonetic level. This work will have implications for current models of speech perception and the sensory encoding of speech signals at the earliest stages of perceptual analysis.